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Among all sectors of refrigeration, one of the most affected by the latest international regulations is the domestic refrigeration. Although for it has been suggested some solutions, such as the construction of household refrigerator operating with the hydrocarbons, there remains the need to find a substitute for R-134a. With the aim of finding a s...
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... Both molecules have two carbon atoms and the same kind of bonds, but they differ in quantity of fluorine and hydrogen. R-134a includes four fluorine atoms and R-152a only two; thus R-152a cannot avoid the flammable characteristics minimised by the fluorine atoms. Tab.1 collects their main thermodynamic, safety and environmental properties and Fig. 1 presents their pressure-enthalpy diagram. The most relevant differences between the fluids are: more considerable latent heat of phase-change of R-152a (+53% respect to R-134a at To=-25 °C), higher specific vapour volume of R-152a (+69.9% in relation to R-134a at saturation at To=-25 °C) and lower inclination of isentropic lines of ...
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... the compression phase during the ON cycles, it can be observed in Fig. 7 the differences between the discharge temperatures are small. Considering the lower slope of R- 152a isentropic lines (Fig. 1), this result suggests an improvement of the isentropic efficiency of the compressor. Nonetheless, this result is bonded to the operation of the compressor ...
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... ON/OFF periods of the system up to -6.2%. Furthermore, the reduction of the Post-defrost period has also lead the refrigerator to reduce by -17.8% the energy consumption during that period. Although this last value is higher, it needs to be highlighted that the Post-defrost phase has less impact on the overall energy consumption, as presented in Fig. 10, where it can be observed the percentage contribution of this phase concerning the total energy consumption of the refrigerator. It can also be seen in Fig. 10 that the use of 90 g R-152a even reduces the impact of the defrosting in the 24h operation about R-134a since the energy consumption proportion of this process is decreased in ...
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... during that period. Although this last value is higher, it needs to be highlighted that the Post-defrost phase has less impact on the overall energy consumption, as presented in Fig. 10, where it can be observed the percentage contribution of this phase concerning the total energy consumption of the refrigerator. It can also be seen in Fig. 10 that the use of 90 g R-152a even reduces the impact of the defrosting in the 24h operation about R-134a since the energy consumption proportion of this process is decreased in ...
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... Both molecules have two carbon atoms and the same kind of bonds, but they differ in quantity of fluorine and hydrogen. R-134a includes four fluorine atoms and R-152a only two; thus R-152a cannot avoid the flammable characteristics minimised by the fluorine atoms. Tab.1 collects their main thermodynamic, safety and environmental properties and Fig. 1 presents their pressure-enthalpy diagram. The most relevant differences between the fluids are: more considerable latent heat of phase-change of R-152a (+53% respect to R-134a at To=-25 °C), higher specific vapour volume of R-152a (+69.9% in relation to R-134a at saturation at To=-25 °C) and lower inclination of isentropic lines of ...
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... the compression phase during the ON cycles, it can be observed in Fig. 7 the differences between the discharge temperatures are small. Considering the lower slope of R- 152a isentropic lines (Fig. 1), this result suggests an improvement of the isentropic efficiency of the compressor. Nonetheless, this result is bonded to the operation of the compressor ...
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... ON/OFF periods of the system up to -6.2%. Furthermore, the reduction of the Post-defrost period has also lead the refrigerator to reduce by -17.8% the energy consumption during that period. Although this last value is higher, it needs to be highlighted that the Post-defrost phase has less impact on the overall energy consumption, as presented in Fig. 10, where it can be observed the percentage contribution of this phase concerning the total energy consumption of the refrigerator. It can also be seen in Fig. 10 that the use of 90 g R-152a even reduces the impact of the defrosting in the 24h operation about R-134a since the energy consumption proportion of this process is decreased in ...
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... during that period. Although this last value is higher, it needs to be highlighted that the Post-defrost phase has less impact on the overall energy consumption, as presented in Fig. 10, where it can be observed the percentage contribution of this phase concerning the total energy consumption of the refrigerator. It can also be seen in Fig. 10 that the use of 90 g R-152a even reduces the impact of the defrosting in the 24h operation about R-134a since the energy consumption proportion of this process is decreased in ...
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Citations
... After using R430A, it was found that up to 10.7 % energy efficiency improvement and better environmental performance were theoretically evaluated at condensing temperatures between 40 • C and 60 • C and evaporator temperatures between − 30 • C and 0 • C, as shown in Fig. 3, although the compressor discharge temperature of R430A was found to be 3 to 10 K higher than those of R134a. Maiorino et al. [81,82] and Bolaji [83] conducted some experimental studies on R152a concluding that it is an interesting eco-friendly drop-in replacement of R134a. Chen et al. [84] experimentally measured an average increase in COP of about 26 % by replacing R134a with R152a at the ambient temperature of 22 • C, condenser temperature between 40 • C and 50 • C, pressure ratios from 2 to 4 and refrigerant charge of 250 g. ...
Small-scale vapour-compression systems for refrigeration, air conditioning, and heat pump (RACHP) applications guarantee several essential human needs. The global energy and environmental policies have compelled these solutions to take a new sustainable growth path, i.e., the adoption of low global warming potential (GWP) refrigerants. The working fluids with GWP below 150 as substitutions in vapour-compression systems across six main applications have been exhaustively reviewed, and focus is given to the aspects of system performance, environmental impacts, operating conditions, and cost. Due to the negligible environmental impacts, natural refrigerants are prioritized to be selected as alternatives to high-GWP synthetics. R744 and R290 are the two most popular natural refrigerants employed across all applications. Compared with using R134a, R744 systems can save energy consumption by up to 37% in commercial refrigeration units while R290 systems can provide higher efficiencies for space heating at low ambient temperatures. R600 and R600a are used in domestic appliances to decrease energy consumption by up to 18.6% and to reduce flammability risks while mixing with R290. R1234yf, as a hydrofluoroolefin (HFO) with negligible-GWP, has been widely used as a substitution in mobile air-conditioning (MAC), although it is under pressure as currently classified as per-fluorinated alkylated substance (PFAS).
... refrigeration system were 330.78 kJ/kg and 216.26 kJ/kg, respectively (Maiorino et al. 2018). Based on the cooling capacity calculation in Eq. (5), larger enthalpy difference between the evaporator inlet and outlet indicates that R152a exhibits a higher cooling capacity than R134a at the same mass flow rate. ...
In light of the adverse environmental impact of the R134a refrigerant, replacing it with a more environmentally friendly refrigerant has become imperative than ever. This study presents an experimental investigation into the utilization of R152a and R134a refrigerants in a vapor compression refrigeration system employing a variable displacement oil-free linear compressor. The potential for the replacement of R134a with R152a was examined based on energy, environmental, and economic performance analyses. The outcomes indicated that R152a exhibited a higher coefficient of performance (COP) in comparison to R134a under identical operating conditions. Specifically, when the pressure ratio was 2.0 and the piston stroke was 11 mm, R152a’s COP was 13.0% higher than R134a. It was also discovered that reducing the operating stroke and increasing the pressure ratio could effectively lower CO2 emissions and total costs. Under the 2.0 pressure ratio and 9-mm piston stroke, R134a produced 1082.4 kg more CO2 emissions than R152a, representing a 209% increase. In addition, the R152a and R134a total cost was reduced by 8.3% with the 2.5 pressure ratio and 11-mm piston stroke. Notably, the results of the current study demonstrated that R152a outperformed R134a in energy consumption, environmental friendliness, and economy in oil-free linear compressor refrigeration systems. R152a used less electric power, generated fewer CO2 emissions, and naturally reduced predicted running costs in order to maintain the same COP.
... The results indicate that the discharge temperature of the compressor and energy consumption is 13.40 C and 28.9% lower when compared with R134a. Choedaeseong et al. 33 investigated the performance of R435A (a combination of DME and R152a) as a replacement for R134a in-home water purifiers. In comparison to HFC 134a, the electricity usage and release temperatures were respectively 12.7% and 3.7 °C lower. ...
Dimethyl ether (DME) and its blend of refrigerants (R429A, R435A, and R510A) are considered in this study's second law analysis as potential replacements for R134a. The performance of various refrigerants in a vapour compression refrigeration system is examined using the Design package CYCLE D. The software REFPROP 9.0 is used to extract all of the thermal and physical parameters of DME and its blend of refrigerants. The Second law performance parameters such as Efficiency Defects, Entropy generation and ExergyEfficiency are discussed. The refrigerants R429A and R510A are more energy efficient than R134a across a condensing temperature range of 30 to 55 °C at − 10 °C evaporation temperature. R134a was exceeded by R429A and R510A in terms of exergetic efficiency by 2.08 and 0.43%, respectively. In comparison to other losses in different components, the compressor's exergy loss is larger at 37–40% of the total exergy loss. By employing RE170 and its blends, the Vapour Compression Refrigeration System often performs better under the second law than R134a.
The result shows that the efficiency defects in the compressor are the largest, followed by the condenser and evaporator. Thus, the design improvement of a compressor is of at most importance to improve the system performance by lowering the overall irreversibility.
... It was reported from this study that alternative refrigerants for high pressure applications are limited. An opportunity to use R152a as an alternative for R134 has also been proposed to find the best charge for the substitute [4]. Also, a study on a heat pump water heater has been carried out to find the best substitute for R410a. ...
Dimethyl ether is one of the derivative products of coal that will be used as a household fuel substitute for LPG in Indonesia. In addition, it can also be used as a working fluid in a refrigeration system. To understand the behavior of this refrigerant, a simulation was carried out to determine the flow pattern of dimethyl ether in a horizontal evaporator. This study was applied in an evaporator of an air conditioner with inside diameter of 6.3 and 7.9 mm and cooling capacity of 2.64 and 5.28 kW. By varying the evaporation temperature from -20 to 5°C it was observed that the flow pattern was dominated by annular flow when the evaporation temperature was set at higher value. Simulation using pipe diameter of 7.9 mm and cooling capacity of 2.64 kW showed that at the evaporator inlet the flow pattern is combination of stratified-wavy and wavy-annular for all range of evaporation temperature. When the pipe diameter was reduced to 6.3 mm, stratified wavy at the evaporator inlet was only found at evaporating temperature of -15 and -20°C. All stratified wavy flow vanishes when the cooling capacity was doubled to 5.28 kW. Annular flow is dominant under this condition.
... ... (23) where the rates of entropy generation for the generator, condenser, expansion device and evaporator are S gen,gener , S gen,con , S gen,expan and S gen,evpo in kJ/h-K, respectively. In the vapor absorption refrigeration system, ammonia is used as refrigerant and the specific heats of ammonia for the liquid and vapor phases have been taken as 4.744 and 2.175 kJ/kg-K, respectively. ...
Entropy generation minimization and exergy destruction minimization concepts are applied on various refrigeration systems. For comparative analyses, coefficients of performance, exergy destruction and entropy generation rates are found for refrigeration systems at same atmospheric conditions. They are also calculated for individual components of each refrigeration system and for various other systems. After analyses, 2.27 coefficient of performance is found for vapor compression refrigeration system, which is maximum among such systems. As maximum exergy destruction and entropy generation rates are obtained for compressor, i.e., 386.07 kJ/h and 1.288 kJ/h-K, minimum rates are found for evaporator. Maximum total destruction and generation rates are recorded for water cooling refrigeration system, but minimum total destruction and generation rates are estimated for vapor absorption refrigeration system. A comparison of vapor compression and absorption refrigeration systems is done, and it is concluded that absorption system performs better on the basis of entropy generation and exergy destruction minimization theories (i.e., minimum 39.332 kJ/h and 0.131 kJ/h-K). It is also found that maximum destruction ratio (i.e., 0.999) is calculated for compressor, so irreversibilities or losses must be reduced by perfect designing of compressor.
... Therefore, different technical solutions for refrigeration systems have been investigated over the last years. Among these, many researchers have been focused on the evaluation of the performance of alternative low-GWP refrigerants, including hydrocarbons (HC), such as isobutane (R600a) and propane (R290); natural refrigerants, such as carbon dioxide (R744) and ammonia (R717); hydro-fluoro-olefins (HFOs); and their mixture with HFCs, such as R1234yf, R1234ze, R450a and R513a among others [3][4][5][6][7]. The main target of the last studies about these possible replacements was to investigate the performance of these fluids as refrigerants and potential improvement which could increase them with the aim to get closer to the performance of HFC refrigerants, ensuring comparable cost with current solutions. ...
... The downstream structure (Figure 4c) is the specular component of the upstream structure, and it is characterized by the discharge tubes exiting by the core structure, a manifold, which brings together the different refrigerant flows by adiabatic mixing, and the outlet tube of the gas cooler, which leads the refrigerant to the expansion element. The mass flow rate of the refrigerant exiting the gas cooler is calculated as shown in Equation (5). Instead, its thermodynamic properties, which represents the output of the entire numerical model, are calculated as a weighted average of the different mass flow rate in each discharge tube. ...
Carbon dioxide trans-critical refrigeration systems have been deeply investigated over the last years, with the aim to improve their performance by using several possible technical solutions. However, most of them lead to a more complex and expensive system, and therefore a trade-off is always needed to identify the best viable solution. Therefore, many efforts have also been focused on the study of a critical component of the basic carbon dioxide trans-critical cycle, which is the gas cooler, especially by numerical simulations. This work shows a new flexible approach to numerically model an air-cooled finned-tube CO2 trans-critical gas cooler integrating a Top-Down methodology with a Finite Difference Method to solve the governing equation of the thermodynamic processes involved. The model was developed to reproduce the behavior of an experimental CO2 refrigeration system, which provided the experimental data used for its validation. In detail, the model showed a good agreement with the experimental data, with average deviations of 1 K (0.3%), 0.9 bar (1%) and 0.15 kW (2.8%) regarding the refrigerant outlet temperature, the refrigerant outlet pressure and the rejected heat, respectively. The Top-Down numerical approach slightly outperformed the performance of previous numerical models available in the literature. Furthermore, the analysis of the refrigerant temperature and pressure along the tubes and rows also shows that the model can reproduce their behavior consistently and accordingly to data reported in the literature. The proposed approach can be used for detailed thermo-economic analysis of the whole refrigeration system, with the aim to optimize the design of the gas cooler.
... Polyolester oil (POE) with viscosities ISO 15-220 is suitable for piston and screw compressor of 1 3 82 Page 2 of 18 the industrial and household refrigeration system. Maiorino et al. [9],analyzed the domestic refrigerator with R-152a as an alternative refrigerant to R-134a and manufacturer's refrigeration lubricant (POE 68). They revealed that R-152a is completely miscible with POE68 and the coefficient of performance was improved by 8.0% using R-152a/POE68 over R134a/POE68 combination. ...
... This finding is harmonious with the improvement of friction results, which are the soundest for BIO50. Maiorino et al. [9] acknowledged that the alternate refrigerant R-152a with POE68 refrigeration oil in domestic refrigerator have a significant increase in COP of about 8.0% as compared with R-134a and POE68 owing to + 2 °C increase in an evaporating temperature. Figure 10c shows the compressor shell temperature when refrigerator is operated under various refrigeration oil samples. ...
The present investigation is aimed at finding the suitability of using vegetable oil-based polyol ester as biodegradable refrigeration oil. Rapeseed oil-based pentaerythritol ester was synthesized via successive trans-esterification route. The formulation was blended with synthetic refrigeration oil (POE68) in the fractions of 25%, 50% and 75% by volume. The tribological investigation involving various refrigeration oils was done using the four-ball tribometer. This study further quantifies the influence of biodegradable refrigeration oils on the performance of domestic refrigerator compressor using vapour compression refrigeration test setup. The process of tribological analysis brought to light the comparable anti-friction and excellent wear reduction behaviour with the blended refrigeration oil sample (BIO50—i.e., 50% by vol. of pentaerythritol ester of rapeseed oil and 50% by vol. of POE68). It was noticed that the BIO50 had considerable rise in coefficient of performance (COP) of about 41.7% and prime impact on the performance of refrigeration compressor. The outcome of the experimental study is supportive in finding vegetable oil-based refrigeration oil to substitute partially the synthetic grade for the domestic refrigerator compressor.
... As a result, they stated that the capacity of R1234yf / R134a is similar to R134a and the COP value of R1234yf/R134a was 4-16% lower than that of R134a (Meng vd., 2018). Maiorino et al. (2018) compared R134a and R152a used in home refrigerators theoretically and experimentally. It has been stated that if R152a is used instead of R134a, there will be a decrease in the total refrigerant charge and energy consumption (Maiorino vd., 2018). ...
ABSTRACT The refrigerants used in the cooling industry and released to the atmosphere cause environmental problems. In the field of refrigeration and air conditioning, the use of chlorofluorocarbons and hydrochlorofluorocarbons is the main cause of ozone depletion and global warming. Replacing hydrofluorocarbons used as refrigerants and refrigerants with low global warming potential (GWP) is among the priority issues in preventing environmental problems. In this study, energy parameters of R450A and R134a refrigerants composed of R134a / R1234ze (E) mixture with low GWP ratio which can be used as an alternative to R134a were analyzed theoretically and environmentally. Two different evaporator temperatures (-15 0 and 15 0 C) and condenser temperatures (35 0 C) were taken into account in the parameter analysis.
... As a result, they stated that the capacity of R1234yf / R134a is similar to R134a and the COP value of R1234yf/R134a was 4-16% lower than that of R134a (Meng vd., 2018). Maiorino et al. (2018) compared R134a and R152a used in home refrigerators theoretically and experimentally. It has been stated that if R152a is used instead of R134a, there will be a decrease in the total refrigerant charge and energy consumption (Maiorino vd., 2018). ...
The refrigerants used in the cooling industry and released to the atmosphere cause environmental problems. In the field of refrigeration and air conditioning, the use of chlorofluorocarbons and hydrochlorofluorocarbons is the main cause of ozone depletion and global warming. Replacing hydrofluorocarbons used as refrigerants and refrigerants with low global warming potential (GWP) is among the priority issues in preventing environmental problems. In this study, energy parameters of R450A and R134a refrigerants composed of R134a / R1234ze (E) mixture with low GWP ratio which can be used as an alternative to R134a were analyzed theoretically and environmentally. Two different evaporator temperatures (-15 0 and 15 0 C) and condenser temperatures (35 0 C) were taken into account in the parameter analysis.
... Regarding the potential alternatives to HFC-134a, Maiorino et al. [21] proposed R-152a as alternative low GWP refrigerant for domestic refrigerators, showing refrigerant charge and energy consumption reductions. Mota-Babiloni et al. [22] performed a drop-in replacement of HFC-134a with HFO-1234yf and HFO-1234ze(E) in vapour compression liquid chiller, proving that the HFC-134a can be replaced by both very low GWP hydrofluoroolefins (HFOs). ...
This study illustrates the potential of high temperature heat pumps (HTHPs) integration into district heating network (DHN) through a twofold approach, using DHN as a heat sink and source. It is used as a heat sink of HTHP that uses waste heat from the supermarket’s refrigeration system as a heat source whereas it is used as a heat source to HTHP that provides heat to industrial applications. When the DHN acts as the heat sink, the integrated system provides a coefficient of performance (COP) of the waste heat recovery (WHR) system between 3.2 and 5.4, reducing the operating costs between 50% and 100% with an average price ratio of 2.25 compared with the standard CO2 refrigeration system. If the DHN is the heat source, the integrated system provides a COP from 2.8 to 5.7 for a heat sink of 110 °C. The alternative low-GWP refrigerants assessment illustrates that HC-290, HFO-1234ze(E) and HFO-1234yf were considered the ideal candidates to replace the HFC-134a, whereas HCFO-1233zd(E) and HCFO-1224yd(Z) were the most promising low-GWP refrigerants to replace HFC-245fa. Finally, the environmental results showed that the utilisation of the DHN as the heat sink in the integrated system solution produces about 60% lower equivalent CO2 emissions than the DHN generation mix. Moreover, using DHN as the heat source, the equivalent CO2 emissions can be reduced up to 98% in Sweden compared to conventional natural gas boilers. Hence, the combination of HTHPs and the DHN represents a step forward in the mitigation of climate change through the utilisation of sustainable energy conversion technologies.
